Geometrical drawing, projection drawing, freehand and ornamental drawing, wash work and brush drawing, elementary perspective drawing, architectural drawing (1921)
International Correspondence Schools · Scranton, PA : International Textbook Co. · leaf 71
e of intersectionwill be a parabola, as at ^h i;but, if, instead of being par-allel to the side be, the cuttingplane makes an angle with it,the curve formed by the inter-section will be either an ellipseor a hyperbola, according to theangle. It will be an ellipsewhen the cutting plane is morenearly… … Fig. 47 §1 GEOMETRICAL DRAWING 57 perpendicular to the base than it was in the case of theparabola, as shown at lm7i and opq. 44. In the case of the hyperbola, the plane will alwayscut both cones, thereby giving two branches to the curve andthese branches will be farther apart as the cutting…
